Dynamic-braking controller.



- C. T. HENDERSON.

DYNAMIC BRAKING CONTROLLER.

APPLICATION FILED OCT. 2. 1913.

1,154,016. Patented Sept. 21, 1915.

aver v13 UNITED STATES PATENT OFFICE."

CLARK '1. HENDERSON, OF MILWAUKEE, WISCONSIN, ASSIGNOR TO THE CUTLER-HAMMER MFG. CO., 01 MILWAUKEE, WISCONSIN, A CORPORATION OF WISCONSIN.

' DYNAMIC-BRAKING CONTROLLER.

Specification of Letters Patent.

Patented Sept. 21, 1915.

Application filed October 2, 1913. Serial No. 793,065.

To all whom it may concern:

I Be it known that I, CLARK T. HENDER- SON, acitizen of the UnitedStates, residing at Milwaukee,-in the county of Milwaukee and State ofWisconsin, have invented new and useful Improvements in ,Dynamic-Braking Controllers, of which the following is a full, clear, concise,and exact description, reference being had to the accompanying'drawing,forming a part of this specification. f 1

My invention relates to improvements in dynamic braking controllers foralternating current motors. It is particularly applicable topontrollerssuch as that disclosed in my co-pending application, SerialNo. 520,128, filed Sept. 29, 1909, but may be advantageously employedwith other forms of controllers.

Oneof the objects of the invention is to provide means insuringmaintenance of the dynamic braking connections until the motor isbrought substantially to rest or its speed reduced to a predetermineddegree.

A further object is to provide for automatic interruption of the dynamicbraking connections at the proper time.

A further object is to provide, in conjunction with the dynamic brake, amechanical brake and means for withholding the mechanical brake untilthe motor is brought substantially to rest or to the desired speed andfor efiecting automatic setting thereof at the proper time.

' Variousother objects and advantages of my invention will appearhereinafter.

For the purpose of more fully and clearly disclosing the nature andadvantages of my for dynamic braking, and other switches controllingresistance in the rotor circuit of themotor for both acceleration anddynamic I braking. Also, it is provided with a mechanical brake but thebrake is controlled in a different manner;

The motor is diagrammatically illustrated as provided with a stator Sand a rotor R. Electro-responsive switches 1, 2 and 3 are provided toconnect the stator to an alternating current circuit A. C., whileelectroresponsive switches 4 and 5 are provided for connecting thestator to a direct current circuit, D. C. Electro-responsive switches 6,7 and 8 are provided for controlling sets of resistances 1', 1" and r inthe rotor circuit of the motor. All of these switches are under thecontrol of a master switch 9 movable in one direction to energizeswitches 1, 2, 3, 6, 7 and 8 to start and accelerate the motor and in anopposite direction to energize switches 4, 5, 6, 7, and 8 for dynamicbraking. As will be understood the connection of the stator to the D. C.circuit establishes a stationary field for the motor, whereby when therotor is driven it generates a dynamic braking current in the rotorcircuit and that by varying the resistance in the rotor circuit thedynamic braking current may be regulated go regulate the dynamic brakingefiect on he motor.

The drawing also shows schematically a mechanical brake 10 having areleasing winding 11 controlled by auxiliary switches 12 and 13 onelectro-responsive switches 2 and 4 respectively. The arrangement issuchthat when the switch 2 responds to connect the motor to the A. C.circuit it energizes the brake coil 11' while the switch 4 on the otherhand, is connected to the rotor v circuit of the motor, and ispreferably provided with one coil for each phase of said rotor circuit.As shown, the rotor circuit is three-phase and the magnet 16 is providedwith three coils having star connections with the rotor circuit. V

The relay 14 responds to the master controller to energize the switches4 and 5 for dynamic braking and upon responding is held by the magnet16. The magnet 16 bein connected as described to the rotor circult, isenergized by the dynamic braking current and accordin lyholds the relayin operative position independently of the operating winding 15. Itinsures maintenance of the dynamic braking connections until the dynamicbraking current decreases to such a value as to render the magnet 16ineffective. Hence, by proper design of the magnet 16 the same may becaused to hold the relay until the dynamic braking current is reduced toany predetermined value and the speed of the motor reduced to acorresponding value. In practice, the magnet 16 is preferably sodesigned as to hold the relay and thus maintain dynamic brakingconnections until the motor is brought substantially to rest.

As will-now be obvious the relay 14 also insures the withholdingof themechanical brake until the motor has been slowed down to the desiredspeed and the dynamic braklng connections thus interrupted. Asheretofore set forth, the release coil 11 of the brake is maintainedenergized so long as the switch 4 remains closed and hence so longas'the relay 14 remains closed. When, however, the relay 14 is releasedand the switch 4 is deenergize'd the brake coil 11 is likewisedeenergized, thereby causing-automatic setting of the brake 10 at thedesired time. Thus, regardless of theoperation of the master controllerthe dynamic braking connections, when once established, are maintainedand the mechanical brake withheld until the motor is broughtsubstantially to rest or reduced to a predetermined speed, whereupon thedynamic braking connections are interrupted and the mechanical brakeset.

The circuit connections of the controller illustrated will now be moreparticularly described: The rotor circuit and the connections of thestator to the A. C. circuit by the switches 1, 2, and 3, are shown inheavy lines and are so obvious as to require no description. The statorconnections established by'the switches 4 and 5 are as follows: from theleft hand side of the D. C. circuit, through switch 4, by conductors 20and 21, through the stator S, by conductor 22, through switch 5 andthence to the right hand side of the D. C. circuit.

The master switch has a contact finger 23 and a coiiperating segment 23providing a permanent connection to one side of the D. O.

circuit. In addition it has contact fingers 24, 25, 26, 27, and 28 withwhich coiiperate two sets of contact fingers. One set includes segments24, 26 27, and 28 and the other includes segments 25", 26", 27", and28". As shown, the master controller is in off position and in thisposition the segments 26",

27 and 28 engage contacts 26, 27, and 28 24 and finger 24, by conductor31 through the operating windings of switches 1, 2, and 3 in parallel,to conductor 32 and thence to the right hand side of the supply circuit.Continued movement of the controller then successively connects contactfingers 26, 27, and 28 through their respective segments, to

segment 23, thereby energizing the wind-.

ings of switches 6, 7, and 8 through conductors 33, 34' and 35respectively. These operating windings have a common return byconductors 36, 37, and38 through auxiliary switch 12 of switch 2, byconductor 39 to the left hand side of the :D. C. circuit. The brake coil11 is energized immediately upon closure of switch 2, the circuit ofthis coil extending from conductor 30 by conductor 40 through said coil,by conductors 41 and 42to conductor 38 and thence to the supply line, asjust traced. This, of course, provides for starting and accelerat ng themotor.

Assume now that the controller is moved to cause engagement of segment25" with I contact finger 25. This results in deenergizing switches 1,2, 3, 6, 7 and 8 and energiz- 'ing operating coil 15 of relay 14-. Thecircuit of the coil 15 is completed from conductor 30 through contactfinger 23, segment 23, segment 25", finger 25, byconductor 43 throughsaid w1nding,by conductor 44 to the left hand side of the D. C.circuit.- The relay 14 thereupon responds, com leting the circuits ofthe operating win ings of switches 4 and 5 from conductor 30 byconductor 45, through said relay -switch, by conductor 46 through saidwindings in parallel, to the-left hand side of the D. C. circuit. Theswitches 4 and 5 thereupon respond, connecting the stator of the motorto the D. C. circuit and completing .'the circuit of the brake coil 11from conductor 41 through auxiliary switch 13, by conductor 50 toconductor 39.- In the meantime, segments 26", 27, and 28 have engagedfingers 26, 27; and 28 and accordingly when the switch 4 closes switches6, 7, and 8 are energized as before described, except that their returncircuit extends from non ductor 37 through auxiliary switch 13 of switch4 instead of auxiliary switch 12 of switch 2. Under these conditions themotor acts as a dynamic brake and all of the resistance is excluded fromthe rotor circuit. If now it is desired to regulate the dynamic brakingcurrent, this can be accomplished by continuing the movement of thecontroller to successively disengage segments 28, 27", and 26 from theircorresponding contact fingers, thereby successively reinserting' theresistances 1', 1" and r in the rotor circuit.

The three terminals of the retaining magnet 16 are connected byconductors 51, 52 and 53 to the three phases of the rotor circuit, andaccordingly said magnet is subjected to the dynamic braking current inall phases of the rotor circuit. When the relay 14 is released itdeenergizes switches 4 and 5 and switch 4, upon opening, denergizes thebrake coil 11 and the operating windings of switches 6, 7 and 8 throughthe medium of its auxiliary switch 13.

What I claim as new and desire to secure by Letters Patent is:

1. The combination with an alternating current motor, of alternating anddirect current sources, means operable to connect said motor to saidalternating current source for running, means operable to connect saidmotor to said direct current source for dynamic braking but tending todisconnect said'motor therefrom and holding means for said lastmentioned means responsive to the dynamic braking current.

2. The combination with an alternating current motor, of direct currentand alternating current sources, means for connecting said motor to saidalternating current source for running and means t'or connecting saidmotor to said direct current source for dynamic braking, saidlast-mentioned means being maintained efi'ective by the dynamic brakingcurrent and automatically interrupting the direct current connectionswhen the dynamic braking current falls below a certain. limit.

3. The combination with an alternating current motor, of separatesources of current, means for connecting said motor to one of saidsources for runnlng, electro-responsive means for connecting said motorto the other of said sources for dynamic braking, saidelectro-responsive means when deenergized tending to disconnect saidmotor'from said latter source, manual means for controlllng saidelectro-responsive means at troller, in combination, a switch foreffecting stator connections for dynamic braking, and a retaining magnetfor said switch energized by the dynamic braking current generated inthe rotor circuit.

5. The combination with an'alternating current motor, of a source ofalternating current, a source of direct current, means for connectingsaid motorto said sources selectively for running and for dynamicbraking, an electrically controlled mechanical brake for said motor tobe energized fromsa'id 30 source of direct current and controlling meansfor said brake including an electroresponsive device responsive to'thedynamic braking current of said motor to maintain said brake inoperativeuntil said motor is substantially brought to rest.

6. The combination with an alternating current motor, of a source ofalternating current, a source of direct current, means for connectingsaid motor to said sources selec-v lagainst interruption of saidconnections and application of said mechanical brake until the motor isbrought substantially to-rest.

8. The combination with an alternating current motor, ofelectro-responsive means for establishing dynamic braking connectionstherefor, an electrically controlled mechanical brake, and meanscontrolled by the dynamic braking current generated by said motor tocontrol both of said former means. 9. The combination with analternating current motor, of electro-responsive means for establishingdynamic braking connections therefor, an electrically controlledmechanical brake, and means governed by the dynamic braking current toinsure the maintenance of said connections and the withdrawal of saidmechanical brake until the motor is brought substantially to rest andthen effecting automatic interruption of said connection and applicationof said mechanical brake. 10. In a controller for alternating currentmotors, in combination, means for establishing dynamic brakingconnections for the motor, and means for maintaining said former meanseiiective including an electro- 130 the operation of said former means,said relay having an operating Winding and a retaining magnet, saidmagnet being connected in the rotor circuit.

12. In a controller for alternating current motors, incombination,means. for connect ing the stator of the motor to a source of directcurrent for dynamic braking, an electrically controlled mechanicalbrake, controlled by said former means, and a. relay controlling theoperation of said first-mentioned means and being governed by thedynamic braking current generated by the motor.

In witness whereof, I have hereunto subscribed my name in the presenceof two witnesses.

- CLARK T. 'HENDERSON. Witnesses: FRANK H. HUBBARD, JEANETTE S. BROOK.

